scholarly journals A Cycle Slip Detection Framework for Reliable Single Frequency RTK Positioning

Sensors ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 304 ◽  
Author(s):  
Salma Zainab Farooq ◽  
Dongkai Yang ◽  
Echoda Ngbede Joshua Ada
Keyword(s):  
Carrier Phase ◽  
Measurement Errors ◽  
Statistical Tests ◽  
Measurement Data ◽  
Single Frequency ◽  
Adjustment Process ◽  
Common Source ◽  
Detection Scheme ◽  
Cycle Slips ◽  
Phase Cycle

Single frequency real-time kinematic (RTK) positioning is expected to be the leading implementation platform for a variety of emerging GNSS mass-market applications. During RTK positioning, the most common source of measurement errors is carrier-phase cycle slips (CS). The presence of CS in carrier-phase measurements is tested by a CS detection technique and correspondingly taken care of. While using CS prone measurement data, positioning reliability is an area of concern for RTK users. Reliability can be linked with the CS detection scheme through a least squares (LS) adjustment process. This paper proposes a CS detection framework for reliable RTK positioning using single-frequency GNSS receivers. The scheme uses double differenced measurements for CS detection via LS adjustment using a detection, identification, and adaptation approach. For reliable positioning, the procedure to link the detection and identification stages is described. Through tests conducted on kinematic data, internal and external reliability are theoretically determined by calculating minimal detectable bias (MDB) and marginally detectable errors, respectively. After introducing CS, the actual values of MDB are found to be four cycles, which are higher than the theoretically obtained values of one and two cycles. Although CS detection for reliable positioning is implemented for single-frequency RTK users, the proposed procedure is generic and can be used whenever CS are detected through statistical tests during LS adjustment.

scholarly journals Carrier Phase-Based Precise Heading and Pitch Estimation Using a Low-Cost GNSS Receiver

2021 ◽  
Vol 13 (18) ◽  
pp. 3642
Author(s):  
Wei Ding ◽  
Wei Sun ◽  
Yang Gao ◽  
Jiaji Wu
Keyword(s):  
Carrier Phase ◽  
Measurement Errors ◽  
Low Cost ◽  
Installation Space ◽  
Estimation Methods ◽  
Single Frequency ◽  
Cycle Slip ◽  
Pitch Estimation ◽  
Gnss Receiver ◽  
Mean Square Errors

Attitude and heading estimation methods using the global navigation satellite system (GNSS) are generally based on multi-antenna deployment, where the installation space and system cost increase with the increase in the number of antennas. Since the single-antenna receiver is still the major choice of the mass market, we focus on precise and reliable heading and pitch estimation using a low-cost GNSS receiver. Carrier phase observations are precise but have an ambiguity problem. A single difference between consecutive epochs can eliminate ambiguity and reduce the measurement errors. In this work, a measurement model based on the time-differenced carrier phases (TDCPs) is utilized to estimate the precise delta position of the antenna between two consecutive epochs. Then, considering the motion constraint, the heading and pitch angles of a moving land vehicle can be determined by the components of the estimated receiver delta position. A threshold on the length of the delta position is selected to avoid large errors in static periods. To improve the reliability of the algorithm, the Doppler-aided cycle slip detection method is applied to exclude carrier phases with possible cycle slips. A real vehicular dynamic experiment using a low-cost, single-frequency GNSS receiver is conducted to evaluate the proposed algorithm. The experimental results show that the proposed algorithm is capable of providing precise vehicular heading and pitch estimates, with both the root mean square errors being better than 1.5°. This also indicates that the cycle slip exclusion is indispensable to avoid unexpected large errors.

scholarly journals Detecting Cycle Slips in Carrier-Phase Measurements of Single Frequency Navigation Receivers with Different Instabilities of Reference Oscillators

2021 ◽  
Vol 5 (2) ◽  
pp. 144-161
Author(s):  
A. S. Pustoshilov ◽  
◽  
S. P. Tsarev ◽  
Keyword(s):  
Carrier Phase ◽  
Single Frequency ◽  
Navigation Systems ◽  
Noise Component ◽  
Phase Measurements ◽  
Additional Information ◽  
Cycle Slips ◽  
Reference Oscillator ◽  
The Difference ◽  
Polynomial Filtering

The use of carrier-phase measurements significantly increases the accuracy of solutions when using the measurements of navigation receivers. One of the problems in carrier-phase measurements is discontinuities (cycle slips) in the measurements. The existing algorithms of detection and compensation of cycle slips in carrier-phase measurements of a singlefrequency navigation receiver either require additional information (for example, Doppler measurements), or operate only in differential mode, or can only detect large cycle slips. The purpose of the research is the development of algorithms for detecting small cycle slips in carrier-phase measurements of single-frequency receivers without using additional information. We use methods of filtering of the trend in the carrier-phase measurements using polynomial or adaptive bases, as well as modified sparse recovery algorithms to estimate cycle slips in the difference between code and carrier-phase measurements. The algorithm which is used to search cycle slips in carrier-phase measurements depends on the quality of the reference oscillator of the navigation receiver. For receivers with high-stability reference oscillators (e.g. active hydrogen maser), one can use polynomial filtering of the trend, the filtering result directly detects discontinuities in carrier-phase measurements with a probability close to unity. For navigation receivers with low-stability reference oscillators (quartz reference oscillators), a modified algorithm for minimization of the total variation with filtering of the trend applied to the difference between the code and carrier-phase single-frequency measurements detects discontinuities in 1 cycle slip against the background of the noise component of comparable magnitude with a probability of 0.8. The results may be applied in navigation systems with single-frequency receivers with low stability reference oscillators, as well as in a posteriori processing of receivers’ measurements to correct carrier-phase measurements on the preprocessing stage.

scholarly journals Standalone Velocity Estimation Method for BDS Receiver Based on Improved ARUKF

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Zilong Shen ◽  
Wenxiang Liu ◽  
Jing Peng ◽  
Feixue Wang ◽  
Wei Xiao
Keyword(s):  
Carrier Phase ◽  
Unscented Kalman Filter ◽  
Estimation Method ◽  
Satellite System ◽  
Velocity Estimation ◽  
Cycle Slips ◽  
Selective Fusion ◽  
Phase Cycle ◽  
Receiver Clock ◽  
Receiver Clock Jump

The Carrier-Phase-Derived Doppler (CPDD) observation is an important type of observation for high-precision standalone velocity estimation (SVE) with the BeiDou Navigation Satellite System (BDS) receiver. The CPDD observation is susceptible to receiver clock jump, carrier-phase cycle slips, and multipath error. How to improve the accuracy and reliability of the SVE method based on the CPDD observation has become an urgent problem to be solved. Based on the Velocity Domain Selective Fusion (VDSF) strategy, this paper proposes the VDSF-ARUKF method for accuracy and reliability improvement of the SVE results of the original ARUKF method. In this improved ARUKF method, the CPDD observation and the raw Doppler observation are fused together based on the detection statistic under the framework of the Adaptively Robust Unscented Kalman Filter (ARUKF). Based on actual observations of the BDS receiver, a set of testing experiments were designed to verify the effectiveness of this improved ARUKF method. The experimental results show that the SVE method of the BDS receiver based on the VDSF-ARUKF can improve the accuracy and reliability of the ARUKF SVE results of the BDS receiver. In the case of multidimensional gross errors in the CPDD observations, the VDSF-ARUKF method can still obtain the SVE results with the highest accuracy on the order of several 10−2m/s when compared with the VDFF-ARUKF method and the ARUKF method using the CPDD observations.

scholarly journals DETECTING CYCLE SLIPS IN CARRIER-PHASE MEASURMENTS OF NAVIGATION RECEIVER WITH HIGH STABLE REFERENCE GENERATORS

2021 ◽  
Author(s):  
Aleksandr Pustoshilov
Keyword(s):  
Carrier Phase ◽  
Single Frequency ◽  
Simple Method ◽  
Phase Measurements ◽  
Frequency Measurements ◽  
Cycle Slips ◽  
High Degree

The paper shows a simple method for detecting cycle slips in the carrier-phase measurements (including single frequency measurements) of navigation receivers with highly stable (hydrogen) reference oscillators by using approximation by high-degree polynomials.

scholarly journals An Improved Relative GNSS Tracking Method Utilizing Single Frequency Receivers

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4073 ◽  
Author(s):  
Wenhao Yang ◽  
Yue Liu ◽  
Fanming Liu
Keyword(s):  
Real Time ◽  
Measurement Data ◽  
Base Station ◽  
Global Navigation Satellite Systems ◽  
Single Frequency ◽  
The Novel ◽  
Cycle Slips ◽  
Station Coordinates ◽  
Baseline Solution ◽  
Novel Method

The Global Navigation Satellite Systems (GNSS) becomes the primary choice for device localization in outdoor situations. At the same time, many applications do not require precise absolute Earth coordinates, but instead, inferring the geometric configuration information of the constituent nodes in the system by relative positioning. The Real-Time Kinematic (RTK) technique shows its efficiency and accuracy in calculating the relative position. However, when the cycle slips occur, the RTK method may take a long time to obtain a fixed ambiguity value, and the positioning result will be a “float” solution with a low meter accuracy. The novel method presented in this paper is based on the Relative GNSS Tracking Algorithm (Regtrack). It calculates the changes in the relative baseline between two receivers without an ambiguity estimation. The dead reckoning method is used to give out the relative baseline solution while a parallel running Extended Kalman Filter (EKF) method reinitiates the relative baseline when too many validation failures happen. We conducted both static and kinematic tests to assess the performance of the new methodology. The experimental results show that the proposed strategy can give accurate millimeter-scale solutions of relative motion vectors in adjacent two epochs. The relative baseline solution can be sub-decimeter level with or without the base station is holding static. In the meantime, when the initial tracking point and base station coordinates are precisely obtained, the tracking result error can be only 40 cm away from the ground truth after a 25 min drive test in an urban environment. The efficiency test shows that the proposed method can be a real-time method, the time that calculates one epoch of measurement data is no more than 80 ms and is less than 10 ms for best results. The novel method can be used as a more robust and accurate ambiguity free tracking approach for outdoor applications.

scholarly journals Improving DGNSS Performance through the Use of Network RTK Corrections

2021 ◽  
Vol 13 (9) ◽  
pp. 1621
Author(s):  
Duojie Weng ◽  
Shengyue Ji ◽  
Yangwei Lu ◽  
Wu Chen ◽  
Zhihua Li
Keyword(s):  
Carrier Phase ◽  
Local Area ◽  
Satellite System ◽  
High Accuracy ◽  
Single Frequency ◽  
Baseline Length ◽  
Low Latitude ◽  
Phase Measurements ◽  
Network Rtk ◽  
Global Navigation Satellite

The differential global navigation satellite system (DGNSS) is an enhancement system that is widely used to improve the accuracy of single-frequency receivers. However, distance-dependent errors are not considered in conventional DGNSS, and DGNSS accuracy decreases when baseline length increases. In network real-time kinematic (RTK) positioning, distance-dependent errors are accurately modelled to enable ambiguity resolution on the user side, and standard Radio Technical Commission for Maritime Services (RTCM) formats have also been developed to describe the spatial characteristics of distance-dependent errors. However, the network RTK service was mainly developed for carrier-phase measurements on professional user receivers. The purpose of this study was to modify the local-area DGNSS through the use of network RTK corrections. Distance-dependent errors can be reduced, and accuracy for a longer baseline length can be improved. The results in the low-latitude areas showed that the accuracy of the modified DGNSS could be improved by more than 50% for a 17.9 km baseline during solar active years. The method in this paper extends the use of available network RTK corrections with high accuracy to normal local-area DGNSS applications.

scholarly journals Real-time GNSS precise point positioning for low-cost smart devices

GPS Solutions ◽  
2021 ◽  
Vol 25 (2) ◽  
Author(s):  
Liang Wang ◽  
Zishen Li ◽  
Ningbo Wang ◽  
Zhiyu Wang
Keyword(s):  
Carrier Phase ◽  
Measurement Errors ◽  
Precise Point Positioning ◽  
Low Cost ◽  
Smart Devices ◽  
Dual Frequency ◽  
Static Mode ◽  
Phase Measurements ◽  
Positioning Errors ◽  
Point Positioning

AbstractGlobal Navigation Satellite System raw measurements from Android smart devices make accurate positioning possible with advanced techniques, e.g., precise point positioning (PPP). To achieve the sub-meter-level positioning accuracy with low-cost smart devices, the PPP algorithm developed for geodetic receivers is adapted and an approach named Smart-PPP is proposed in this contribution. In Smart-PPP, the uncombined PPP model is applied for the unified processing of single- and dual-frequency measurements from tracked satellites. The receiver clock terms are parameterized independently for the code and carrier phase measurements of each tracking signal for handling the inconsistency between the code and carrier phases measured by smart devices. The ionospheric pseudo-observations are adopted to provide absolute constraints on the estimation of slant ionospheric delays and to strengthen the uncombined PPP model. A modified stochastic model is employed to weight code and carrier phase measurements by considering the high correlation between the measurement errors and the signal strengths for smart devices. Additionally, an application software based on the Android platform is developed for realizing Smart-PPP in smart devices. The positioning performance of Smart-PPP is validated in both static and kinematic cases. Results show that the positioning errors of Smart-PPP solutions can converge to below 1.0 m within a few minutes in static mode and the converged solutions can achieve an accuracy of about 0.2 m of root mean square (RMS) both for the east, north and up components. For the kinematic test, the RMS values of Smart-PPP positioning errors are 0.65, 0.54 and 1.09 m in the east, north and up components, respectively. Static and kinematic tests both show that the Smart-PPP solutions outperform the internal results provided by the experimental smart devices.

Dynamic Measurement of Spatial Attitude at Bottom Rotating Drillstring: Simulation, Experimental, and Field Test

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Qilong Xue ◽  
Ruihe Wang ◽  
Baolin Liu ◽  
Leilei Huang
Keyword(s):  
Real Time ◽  
Measurement Errors ◽  
Time Window ◽  
Measurement Data ◽  
Movement Patterns ◽  
Dynamic Measurement ◽  
Drilling Process ◽  
Stick Slip ◽  
Actual Measurement ◽  
Gas Drilling

In the oil and gas drilling engineering, measurement-while-drilling (MWD) system is usually used to provide real-time monitoring of the position and orientation of the bottom hole. Particularly in the rotary steerable drilling technology and application, it is a challenge to measure the spatial attitude of the bottom drillstring accurately in real time while the drillstring is rotating. A set of “strap-down” measurement system was developed in this paper. The triaxial accelerometer and triaxial fluxgate were installed near the bit, and real-time inclination and azimuth can be measured while the drillstring is rotating. Furthermore, the mathematical model of the continuous measurement was established during drilling. The real-time signals of the accelerometer and the fluxgate sensors are processed and analyzed in a time window, and the movement patterns of the drilling bit will be observed, such as stationary, uniform rotation, and stick–slip. Different signal processing methods will be used for different movement patterns. Additionally, a scientific approach was put forward to improve the solver accuracy benefit from the use of stick–slip vibration phenomenon. We also developed the Kalman filter (KF) to improve the solver accuracy. The actual measurement data through drilling process verify that the algorithm proposed in this paper is reliable and effective and the dynamic measurement errors of inclination and azimuth are effectively reduced.

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